1. Field of the Invention
This invention relates to a head box in a paper machine, and particularly to a head box in a paper machine in which a perforated plate and a conduction pipe group for dispersing and straightening paper material are disposed between a mixing chamber at a rear end of the head box and a slice lip at a front end of the head box.
2. Brief Description of the Prior Art
A head box has at a rear end thereof a mixing chamber which normally receives a supply of paper material and at a front end thereof a slice lip for flowing paper material onto a paper forming belt. It also has means for dispersing paper material and straightening the material between the slice lip and the mixing chamber. Heretofore, there is known a head box in which, as, a means for dispersing the paper material and straightening thereof, a perforated plate is disposed on the outlet side of the mixing chamber and a group of elongated metal conduction pipes are disposed over generally the entire distance between the perforated plate and the slice lip.
Paper material supplied to the mixing chamber and passed through the perforated plate is further passed through the group of elongated conduction pipes, where the paper material is enhanced to be uniformly dispersed and straightened and given directivity, and then discharged into the slice lip.
The group of conduction pipes and the perforated plate are assembled in the head box in the afore-mentioned arrangement and firmly fixed to a frame for accommodating them.
The group of conduction pipes are expanded and contracted depending on the temperature of the paper material flowing in the conduction pipes, the temperature difference caused by environmental circumstances, etc. Heretofore, however, the group of conduction pipes and the perforated plate are fixed to the frame of the head box and thus unable to be expanded and contracted.
As a consequence, the group of conduction pipes are distorted and deformed due to the thermal expansion and contraction phenomenon, and for this reason, accuracy of the conduction pipes is jeopardized. As a result, the dispersing and straightening functions of the respective conduction pipes are impared, or the stream or flow is not uniform, thereby giving an unfavorable effect to the texture of paper, etc.